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Extend & revamp pg_bswap.h infrastructure.

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Upcoming patches are going to address performance issues that involve
slow system provided ntohs/htons etc. To address that expand
pg_bswap.h to provide pg_ntoh{16,32,64}, pg_hton{16,32,64} and
optimize their respective implementations by using compiler intrinsics
for gcc compatible compilers and msvc. Fall back to manual
implementations using shifts etc otherwise.

Additionally remove multiple evaluation hazards from the existing
BSWAP32/64 macros, by replacing them with inline functions when
necessary. In the course of that the naming scheme is changed to
pg_bswap16/32/64.

Author: Andres Freund
Discussion: https://postgr.es/m/20170927172019.gheidqy6xvlxb325@alap3.anarazel.de
This commit is contained in:
Andres Freund
2017-09-29 15:52:55 -07:00
parent 0008a106d4
commit 510b8cbff1
8 changed files with 159 additions and 27 deletions
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17
config/c-compiler.m4
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@ -224,6 +224,23 @@ AC_DEFINE(HAVE__BUILTIN_TYPES_COMPATIBLE_P, 1,
fi])# PGAC_C_TYPES_COMPATIBLE
# PGAC_C_BUILTIN_BSWAP16
# -------------------------
# Check if the C compiler understands __builtin_bswap16(),
# and define HAVE__BUILTIN_BSWAP16 if so.
AC_DEFUN([PGAC_C_BUILTIN_BSWAP16],
[AC_CACHE_CHECK(for __builtin_bswap16, pgac_cv__builtin_bswap16,
[AC_COMPILE_IFELSE([AC_LANG_SOURCE(
[static unsigned long int x = __builtin_bswap16(0xaabb);]
)],
[pgac_cv__builtin_bswap16=yes],
[pgac_cv__builtin_bswap16=no])])
if test x"$pgac_cv__builtin_bswap16" = xyes ; then
AC_DEFINE(HAVE__BUILTIN_BSWAP16, 1,
[Define to 1 if your compiler understands __builtin_bswap16.])
fi])# PGAC_C_BUILTIN_BSWAP16
# PGAC_C_BUILTIN_BSWAP32
# -------------------------